Cr 250 03 might have landed on something…

[tchui]

Hi, I bought my bike used so im not sure if I am right at all on a possibility of why the 03 is so trouble some on jetting.

Its simple really, we play with head gasket thickness to change the compression ratio, the same can be done with the base gasket as well can it not? I did a top end job the other day and changed the base gasket from whatever was there (pink color) to a cometic one (black color) that is thinner, which would increase my compression (from what it was rightly or wrongly) yes?
As a result the bike has more power (new top end remember) BUT it runs better on idle and low rev with less spooge and a far more brownish plug color.

In fact its ALOT harder (physically) to kick start and alas two head studs pulled out, too much compression? Unless cometic is selling the wrong gaskets I think not, just an old bike and some bad luck.

Just thought id share as it could simply be due to a new top end but, there is a definite difference in the gasket thickness between what was there before and now, happy riding!

[dogger315]

Your observations are correct. It is a well known engine builder's trick to use
different thickness gaskets to "tune" the power curve. Cometic sells stock
as well as performance gaskets. The performance gaskets are a fraction of
a millimeter thinner than stock. This will yield a small jump in the compression
ratio.

As far as upping the compression ratio enough to pull your head studs or
make the bike physically harder to kick over, I believe that was more a
function of refreshing a seriously tired top end and loose head studs.

The good news is you are enjoying the benefits of a fresh top end with
improved response and more power.

dogger